Despite it is commonly known that “smoking is harmful to your health”, the number of smokers worldwide is up to 1 billion, and the number is increasing every year. On Mar. 1, 2003, the World Health Organization (WHO) concluded a global Framework Convention on Tobacco Control. According to the statistical data from WHO, about 4.9 million people die of is diseases caused by smoking each year. Although smoking may cause serious respiratory diseases and cancer, it remains extremely difficult for smokers to quit smoking completely.
The active ingredient in a cigarette is nicotine. During smoking, nicotine, along with a lot of tar aerosol droplets produced in the cigarette burning, enters smoker's alveolus and is rapidly absorbed. After being absorbed into the blood of a smoker, nicotine then produces its effect on the receptors of the smoker's central nervous system, which makes him/her relax and enjoy an inebriety similar to that produced by an exhilarant.
Nicotine is a kind of alkaloid with low molecular weight and its half-life in blood is quite short. The major harmful subsatance in tobacco is tar, tar in tobacco is composed of thousands of ingredients, tens of which are carcinogenic substances. At present it has been proven that passive smoking can be more harmful to non-smokers.
Some cigarette substitutes flat contain only nicotine without tar have been proposed, many of them, such as “nicotine patch”, “nicotine mouthwash”, “spray agent packaged in high pressure gas tank with propellant”, “nicotine chewing gum”, “nicotine drink” etc., are made of pure nicotine. Although these cigarette substitutes are free from tar, their major disadvantage is that an effective peak concentration can not be reached in the blood of a smoker due to slow absorption of nicotine and thus it can not make a smoker get real fin, in addition, these cigarette substitutes can not satisfy habitual smoking actions of a smoker, for example, inhaling action or sucking action, and thus are not likely to be widely accepted as effective substitutes for quitting smoking or cigarette substitutes.